Information
-
Patent Grant
-
6283479
-
Patent Number
6,283,479
-
Date Filed
Thursday, April 8, 199925 years ago
-
Date Issued
Tuesday, September 4, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
- Knight; Anthony
- Hewitt; James M.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 277 591
- 277 592
- 277 650
- 277 652
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International Classifications
-
Abstract
A sealing arrangement improves sealing of a shaft in a control system on a gas turbine engine. The sealing arrangement includes a first plate and a non-metallic plate. The non-metallic plate has a glass transition temperature above an operating temperature range. The non-metallic plate and the first plate are disposed between a high temperature, high pressure fluid and a low pressure fluid.
Description
TECHNICAL FIELD
This invention relates generally to a gas turbine engine and more particularly to a low leakage non-metallic seal interposed a high pressure fluid and a low pressure fluid being positioned about a rotating shaft.
BACKGROUND ART
Gas turbine engine performance is very dependent on maintaining a tight seal between a high pressure region and a low pressure region. These regions are present throughout the gas turbine engine including regions between the turbine stages, compressor stages, and other locations.
To add to the complexity of sealing the high pressure region from the low pressure region, many of the seals in the gas turbine engine are established between moving parts. In one particular application, a shaft seal prevents a hot, high pressure gas from moving between a housing and a rotating shaft into a low pressure gas. Current sealing arrangements such as C-seals, E-seals, bellows seals, and Garlock seals tend to wear quickly. The wear of these seals is further exacerbated by leakage through these seals.
Some manufacturers use a plurality of non-metallic seals in a piston ring fashion. These seals may work well in a low temperature environment. However, the non-metallic seals tend to have reduced mechanical strength at higher temperatures. The reduced mechanical strength allows the seals to lose their shape or fail to return to their original shape. Leaking increases as the seals loose their mechanical strength. At higher temperatures, the leakage rates will oxidize the seal and further increase leakage. In some instances leakage may create problems controlling the gas turbine engine.
The present invention is directed to overcome one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the invention, a seal is formed between a shaft and a housing. The seal has a first plate disposed about a circumference of the shaft and an inner periphery of the housing. The first plate has a first side and a second side. The first side of the first plate is exposed to a low pressure fluid. The first plate has high temperature mechanical strength and is adapted to provide structural support. A non-metallic plate is disposed about the circumference of the shaft and the inner periphery of the housing. The non-metallic plate has a first side and a second side. The first side of the non-metallic plate is adjacent to the second side of the first plate. The second side of the non-metallic plate is adjacent to a high pressure fluid. The non-metallic plate has a glass transition temperature above a predetermined temperature.
In another aspect of the invention, a method is defined for sealing a high pressure fluid on a first side of a shaft from a low pressure fluid on a second side. The high pressure fluid is separated from the low pressure fluid with a non-metallic material having a glass transition temperature above an operating temperature of the high pressure fluid. The non-metallic material is supported structurally to maintain a predetermined shape.
In a further aspect of the invention, a control system for a gas turbine engine has a sealing arrangement. The sealing arrangement has a housing with a first portion and a second portion. The second portion is spaced from the first portion. The first portion is proximate a low pressure fluid. The second portion is proximate a high pressure fluid. A shaft is disposed in the housing. The first seal is disposed proximate the first portion. The first seal is intermediate the shaft and the housing. The first seal has high temperature mechanical strength. A non-metallic seal is disposed intermediate the first seal and the second portion. The non-metallic seal is intermediate the shaft and the housing. The non-metallic seal has a glass transition temperature above an operating temperature of the high pressure fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a partially sectioned view of a gas turbine engine embodying the present invention;
FIG. 2
is a drawing of a fuel injection valve for a gas turbine engine embodying the present invention;
FIG. 3
is a partial cross-sectional view of the fuel injection valve in
FIG. 2
; and
FIG. 4
is a partial cross-sectional view of the fuel injection valve in
FIG. 2
having an alternative embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
As seen in
FIG. 1
, a gas turbine engine
10
has a compressor section
12
, a combustor section
14
, and a turbine section
16
disposed about a central axis
17
. The combustor section
14
in this application is positioned between the compressor section
12
and the turbine section
16
. Both the compressor section
12
and the turbine section
16
fluidly connect with the combustor section
14
. The turbine section
16
and compressor section
12
mechanically connect generally by a shaft (not shown). However, any conventional gearing arrangement may be used.
The turbine section
16
includes a power turbine
18
and a gas producing turbine
20
. The gas producing turbine
20
mechanically connects to the shaft (not shown). The power turbine
18
is connected to a second shaft (not shown) suitable for driving some external accessory (not shown).
The combustor section
14
is defined by an outer housing
22
. The outer housing
22
generally extends between the compressor section
12
and the turbine section
16
. The outer housing
22
has a plurality of regularly spaced openings
24
having a pre-established position in relation to one another. In this application, the openings
24
are positioned around the outer housing
22
near the compressor section
12
. While this application shows an annular type combustor, a plurality of can-type combustors or a can-annular type combustor may also be used without changing the essence of the invention. Each of the regularly spaced openings
24
has a corresponding second regularly spaced opening
26
. A fuel injector
30
passes through each regularly spaced opening
24
into the corresponding second regularly spaced opening
26
.
As shown in
FIG. 2
, the fuel injector
30
is shown having a sealing arrangement
32
, a shaft
34
, a flow restriction device
36
, a fuel injector body
38
, a fuel injector connection portion
40
, and a fuel transfer portion
42
. The fuel transfer portion
42
connects the fuel injector connection portion
40
to the fuel injector body
38
. The fuel injector connection portion
40
connects to the outer housing
22
such that the fuel transfer portion
42
and fuel injector body
38
are inside of the outer housing
22
. The flow restriction device
36
pivotally connects with the fuel injector body
38
. The shaft
34
connects between the flow restriction device
36
and the sealing arrangement
32
. In this application, the sealing arrangement
32
connects with the fuel injector connection portion
40
.
FIG. 3
shows the sealing arrangement
32
having a housing
44
, a bore
46
, valve actuator
48
, a connector
50
, a nut
52
, a first plate
54
, a non-metallic plate
56
, and a graphite plate
58
. While the sealing arrangement
32
is shown for a fuel injector
30
, the sealing arrangement
32
will work with other shaft and housing interactions found in gas turbine engines or other systems where trying to separate hot, high pressure fluid from lower pressure fluid. The housing
44
in this application has a first portion
60
and a second portion
62
. The first portion
60
is exposed to a low pressure fluid
64
. For the particular example, the low pressure fluid
64
may be at atmospheric pressures and temperatures from about −40° F. to 130° F. (−40 C to 54.4 C). In this application the second portion
62
is exposed to a high pressure air
66
ranging in pressure from about 14.7 psia to 235 psia (1.014 kPa to 1620 kPa) and about −40° F. to 640° F. (−40 C to 338 C). The housing
44
has a lip portion
68
proximate the second portion
62
. The lip portion
68
represents one of numerous conventional methods that could be used to secure the graphite plate
58
within the housing
44
. The shaft
34
is generally a circular cylinder having a circumference.
In the embodiment shown in
FIG. 3
, graphite is used as a sacrificial material to prevent oxidation of the non-metallic plate
56
however, other oxidation promoting material may be used such as plain carbon steel. The graphite plate
58
has a first side
70
and a second side
72
. The second side
72
of the graphite plate
58
rests against the lip portion
68
of the housing
44
. In this application all of the plates
54
,
56
, and
58
are disk-shaped having a bore portion adapted to receive the shaft
34
, but other shapes may be used. Each plate
54
,
56
, and
58
is continuous except for the bore portion. The graphite plate
58
initially tightly engages the housing
44
at the periphery of the housing bore. After several rotations of the shaft
58
, the graphite plate
58
loses contact with the shaft
34
. The non-metallic plate
56
has a first side
74
and a second side
76
. The second side
76
of the non-metallic plate
56
is positioned adjacent the first side
70
of the graphite plate
58
. The non-metallic plate
56
tightly engages the housing
44
at the periphery of the housing bore
46
. The bore portion of the non-metallic plate
56
tightly engages the circumference of the shaft
34
.
The non-metallic plate
56
is made of a material having a glass transition temperature above an operating range of about 650° F. (338 C) experienced by the fuel injector
30
. A polyimide going by the trademark VESPEL ST is an example of a material having an infinite glass transition temperature meaning that VESPEL ST will not melt at any temperature. VESPEL ST can be easily machined into numerous shapes. Preferably, the non-metallic plate
56
will also have a coefficient of thermal expansion greater than a coefficient of thermal expansion of the housing
44
.
The first plate
54
has a first side
78
and a second side
80
. The second side
80
of the first plate
54
is adjacent the first side
74
of the non-metallic plate
56
. The first plate
54
has an inside diameter slightly greater than the shaft
34
and slightly smaller than the bore
46
. The first plate
54
in this application may be made of any material exhibiting high mechanical strength in the operating temperature range. Mechanical strength being the ability of a material to retain its shape under mechanical loading including tensile, compressive, and shearing stress. Preferably the first plate
54
is made of a high temperature alloy like stainless steels or nickel alloys such as Inconel, Monel, and Hastelloy. These materials typically retain their tensile strength over wide temperature ranges. Additionally these materials resist oxidation at high temperatures.
The nut
52
is shown in
FIG. 1
threadably engaging the housing
44
and adjacent to the first side
78
of the first plate
54
. This represents only one method of compressing the plates
28
,
30
,
32
into contact with one another. Other conventional methods may also be used such as snap rings. The actuator
64
connects to the shaft
34
through the connector
50
.
An alternative embodiment in
FIG. 4
replaces the graphite plate
58
with either an oxidation prone material
82
or oxidation resistant material placed intermediate the non-metallic plate
56
and the high pressure fluid
66
. In this application, the oxidation prone material
82
is shown as a coating on the non-metallic plate
56
.
Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.
Industrial Applicability
The sealing arrangement
32
reduces leakage of the high pressure fluid
66
to the low pressure fluid
64
along the shaft
34
. In the present embodiment, the sealing arrangement
32
greatly reduces leakage by using the non-metallic plate
56
to prevent leakage between the shaft
34
and the housing
44
. The non-metallic plate
56
differs from normal elastomers or plastics. Typical elastomers and plastics have good resilience at low temperatures. However, these materials begin to flow and loose their shape or disintegrate as the temperature increases past their glass transition temperature. In this application, the non-metallic plate
56
will retain its general shape during normal operating temperatures of the gas turbine engine. The non-metallic plate
56
will, however, start losing its mechanical strength when its temperature is above about 100° F. (37.8 C).
The first plate
54
in association with the graphite plate constrains the non-metallic plate
56
from expanding axially along the shaft
34
. As the temperature increases, the sealing arrangement
32
further improves sealing. The lower thermal expansion of the housing
44
will prevent the non-metallic plate
56
from expanding radially outward. The non-metallic plate
56
will generally expand radially inward and increase interaction between the non-metallic plate
56
and the shaft
34
.
The graphite plate
58
further protects the non-metallic plate
56
by oxidizing prior to the non-metallic plate
56
. Preliminary oxidation of the graphite plate
58
prevents oxygen from reaching the non-metallic plate
56
.
Instead of using the graphite plate
58
, the other embodiments may use either an oxidation prone material
82
on the second side of the non-metallic plate. The oxidation prone material
82
will remove oxygen from the high pressure air
66
prior to contacting the non-metallic plate. In another embodiment, the oxidation resistant material
84
prevents oxygen from contacting the non-metallic plate
56
.
Claims
- 1. A sealing arrangement for a gas turbine engine comprising:a housing having a first portion and a second portion, said second portion being distal from said first portion, said second portion having a lip portion; a shaft being disposed through said housing; a first seal being disposed proximate said first portion, said first seal being intermediate said shaft and said housing, said first seal having high temperature mechanical strength; and a polymeric seal being disposed intermediate said first seal and said second portion, said polymeric seal being intermediate said shaft and said housing, said polymeric seal having a glass transition temperature above a predetermined operating temperature, said polymeric seal being adjacent said lip portion.
- 2. The sealing arrangement as specified in claim 1 further comprising an oxidation prone material disposed intermediate said lip portion and said polymeric seal.
- 3. The sealing arrangement as specified in claim 1 wherein said operating temperature is above 640 F.
- 4. The sealing arrangement as specified in claim 1 further comprising a nut adjacent said first seal, said nut being adapted to hold said first seal in contact with said polymeric seal.
US Referenced Citations (10)